We've had a problem with our garage door opener for a few months now,
and since winter is coming we are using it a lot more. I can't really
afford to call someone out right now, so I've been trying to figure out
what I can do to try to troubleshoot the problem myself. Here is what
I've come up with so far. Does anyone have any suggestions? Might I
be barking up the totally wrong tree? Thanks! -Bob


The problem:

The garage door will not close normally with a single push of the
operation button, or through use of the remote control. To close the
door, we need to hold down the button until the door is completely
closed, otherwise, the door closes a couple of inches and immediately
"bounces" back open.

This situation is unacceptable both because of its inconvenience and
because it's potentially unsafe for our three cats and one two year
old.

The parts:

There is an Allister Access 3000 automatic garage door opener. There
are two screw terminals on the opener have a two-conductor wire
attached that leads to the left side (standing in the garage facing
out) entrapment photo sensor. There is another two conductor wire that
leads to the right side entrapment sensor from the left sensor.

Troubleshooting technique:

1) Using my digital multi-meter, touch one lead against each of the
screw down terminals of the closer and check for any voltage when the
door is attempt to be closed. TODO: see if I can find out what the
expected voltage should be.

2) If I get a voltage measurement on step 1, then check the conductors
going to the left-side sensor for voltage and see if it's similar.
If it's not then I can assume that there is a problem with the cable
run from the closer to the left sensor. If there is, then go to step
3.

3) Check for voltage at the left sensor terminals that lead to the
right sensor. TODO: see if I can find out what the expected voltage
should be here. If I get voltage here, then go to 4.

4) Check the conductors at the right side sensor for voltage. It
should be the same as 3. If it isn't then I can assume the there is
a problem with the cable run from the left sensor to the right sensor.
If it is the same, then go to 5.

5) Assume the problem is either faulty sensors or misaligned sensors.
Is there any way to test the sensors? Perhaps with short speaker cable
runs and holding them directly across from each other?

6) Buy new sensors.